Purpose: Previous gene transfection studies have shown that the accumulation of human ribonucleotide reductase small subunit M2 (hRRM2) enhances cellular transformation, tumorigenesis, and malignancy potential. The latest identified small subunit p53R2 has 80% homology to hRRM2. Here, we investigate the role of p53R2 in cancer invasion and metastasis. Experimental Design: The immunohistochemistry was conducted on a tissue array including 49 primary and 59 metastatic colon adenocarcinoma samples to determine the relationship between p53R2 expression and metastasis. A Matrigel invasive chamber was used to sort the highly invasive cells and to evaluate the invasion potential of p53R2. Results: Univariate and multivariate analyses revealed that p53R2 is negatively related to the metastasis of colon adenocarcinoma samples (odds ratio, 0.23; P < 0.05). The decrease of p53R2 is associated with cell invasion potential, which was observed in both p53 wild-type (KB) and mutant (PC-3 and Mia PaCa-2) cell lines. An increase in p53R2 expression by gene transfection significantly reduced the cellular invasion potential to 54% and 30% in KB and PC-3 cells, respectively, whereas inhibition of p53R2 by short interfering RNA resulted in a 3-fold increase in cell migration. Conclusions: Opposite regulation of hRRM2 and p53R2 in invasion potential might play a critical role in determining the invasion and metastasis phenotype in cancer cells. The expression level of ribonucleotide reductase small subunits may serve as a biomarker to predict the malignancy potential of human cancers in the future.Ribonucleoside diphosphate reductase (RR) plays an essential role in converting ribonucleoside diphosphate to 2 ¶-deoxyribonucleoside diphosphate. In a RR holoenzyme, large a and small h subunits form an a 2 h 2 heterotetramer that is required for RR activity (1). In humans, one large subunit (M1) and two small subunits (hRRM2 and p53R2) of RR have been identified (2). The large subunit M1 (hRRM1) contains substrate and allosteric effector sites that control the RR holoenzyme activity and substrate specificity (3 -5). The RR small subunits form two equivalent dinuclear iron centers that stabilize the tyrosyl free radical required for the initiation of electron transformation during catalysis (3,6). RR is essential as it provides deoxynucleotide triphosphate (dNTP) for DNA synthesis and DNA repair. The expression, subcellular localization, and function of RR are highly regulated (7). Because RR plays a critical role in DNA synthesis, it represents an important target for cancer therapy.Two RR small subunits, p53R2 and hRRM2, have an 80% similarity in protein sequence (2). An in vitro assay showed that recombinant p53R2 protein, as well as hRRM2, interacts with hRRM1 to form a holoenzyme with the ability to convert CDP to dCDP (8, 9). The diiron-dityrosyl radical cluster was identified as the RR activity center, located on the common binding pockets of p53R2 and hRRM2 (10). Using a synthetic heptapeptide to inhibit RR activity, p53R2...

Unique tunable aryl imidazolium ionic liquids successfully catalyzed Friedel–Crafts acylation and thioesterification in sealed tubes. These reactions can form a C−C bond and a C−S bond with high atom economy. Ionic liquids exhibited high activity and catalyzed essential reactions with good to excellent yields while retaining their catalytic activities for recycling.

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This report discloses a mild and efficient O-acetylation using easily accessible TMSOAc as a novel acetyl reagent and O-trimethylsilylation using HMDS for various alcohols catalyzed by tunable Brønsted acidic ionic liquids (TBAILs). Imidazolium-based TBAILs were prepared by a two-step atom-economic reaction and acidities measured by using UV-visible spectroscopy. Both protections for alcohols were accomplished at room temperature with good to excellent yields, while the products and TBAILs were separated by simple work-up for O-silylation and column chromatography for O-acetylation. Notably, with the simple post-process, TBAILs catalyst in this solvent free method easily recovered and recycled several times without significant degradation.

The trimethylsilyl (TMS) group is widely used in carbo­hydrate synthesis, although this protecting group is unstable and its post-synthetic purification challenging. The successful trimethylsilyl­ation of carbohydrates mediated by recyclable and efficient acidic catalyst PTA/HMDS and the novel reagent, TMSOAc (TEA/TMSOAc), under alkaline condition is reported. The advantages of these methods are that the reactions proceed in good to excellent yields without applying column chromatography for purification.